In general, electronic circuitry can be divided into two generally different classes of circuits-analog circuits and digital circuits. Originally, most electronic circuits fell into the analog class. However, in the last few decades a wide variety of digital circuits have been developed for use in various environments, particularly data processing environments. While digital circuits have found widespread use in the processing of data, most, if not all, data sources are analog in nature. Thus, it is necessary to convert measured or detected data from analog form into digital form prior to processing the data. As a result, many electronic systems include both analog and digital circuits.
In the past, separate test equipment has been utilized to test the digital and analog circuits of electronic systems. In this regard, logic analyzers have been developed for testing digital circuits. Logic analyzers test digital circuits by automatically producing one or more digital test signals, applying the digital test signals to a digital circuit to be tested and determining whether or not the digital circuit correctly processes the signals by analyzing either the output of the digital circuit or the signals occuring at predetermined circuit test points. Many logic analyzers are programmable so that a single logic analyzer can be utilized to test a wide variety of different types of digital circuits. Contrariwise, in the past testing analog circuits (regardless of whether or not they are combined with digital circuits in a combined electronic system) has required either the development of specialized automatic test equipment or the application of time consuming manual test procedures using standard test instruments, such as oscilloscopes, voltmeters, ammeters, etc., due to the lack of a single piece of equipment that can be programmed to automatically test in a rapid and efficient manner a wide variety of analog circuits. Obviously, it would be desirable to provide such test equipment. Even more desirable is a single piece of test equipment suitable for testing a wide variety of both analog and digital circuits. One of the problems with providing such a hybrid piece of test equipment has been the difficulty in providing an inexpensive circuit for digitizing analog waveforms, particularly a waveform digitizer that can be readily combined with programmable logic analyzers.
Therefore, it is an object of this invention to provide a waveform digitizer.
It is also an object of this invention to provide a waveform digitizer that is particularly suitable for use in analyzing analog signals.
It is still another object of this invention to provide a waveform digitizer that is relatively inexpensive, yet suitable for use in combination with digital logic analyzers to provide a hybrid analyzer suitable for analyzing both analog and digital signals.
In addition to being above to automatically analyze both digital and analog signals, it is also desirable to be able to display the signals being analyzed, particularly when the signal analysis determines that the circuit being tested is not operating satisfactorily. Such displays are usually provided so that an operator can more easily locate and identify the location of faults in a circuit under test. Usually such displays are produced on a cathode ray tube (CRT) display.
Therefore, it is a further object of this invention to provide a waveform digitizer suitable for producing signals adapted to control a display.
It is yet another object of this invention to provide a waveform digitizer suitable for use in analog and combined analog and digital signal analyzers adapted to analyze analog or both analog and digital signals, respectively, and display the signals being analyzed.